According to Mueller’s data, BT and TalkTalk were the most prolific throttlers of P2P traffic. This will not come as much of a surprise because both have Fair Usage Policies (FUP) that state similar restrictions. Note that we have only included data from four UK ISPs as the sample size for others was simply too small to be reliable (Glasnost can sometimes generate false positives).
It’s worth remembering that the degree to which Traffic Management is used can vary depending upon your package type, broadband platform (LLU, BT, cable etc.) and whether or not you’re running the test(s) during a peak or off-peak period; throttling is more common during busy periods. This is why some tests, even if the ISP uses DPI, won’t always show throttling.